1. Field of the Invention
The present invention relates to a filter unit having cap arrangement providing the ability to close a filter housing containing a filter, in which the cap arrangement has the ability to withstand high pressure.
2. Description of the Prior Art
Filter caps are known for use in providing closure to filter housings. Filter housings are used to hold filters and to direct fluid through them. In the course of operation, residue collects on or in the filter, and the filter housing is opened periodically for the replacement of filters. Filter cap designs accommodate the need for ease in opening the filter housing for inspection or replacement of filters, as well as the need to contain a pressure differential between the inside and the outside of the filter housing. Many current designs make use of a threaded connection between the filter cap and the filter housing; threads bear the load and the threaded assembly can be disassembled easily. It is also common to incorporate o-rings, gaskets or other seals in the cap assembly to prevent fluid from leaking between filter cap and filter housing.
It is known in the art that material contained in the fluid in the filter housing, such as grit, dirt, sludge or other residue, may be carried out of the filter housing during filter replacement and may be deposited on the threads of the filter housing or the filter cap. The result of residue deposit on the threads may be the inability to obtain a leak-tight seal, thread wear or occlusion, or difficulty in removing the filter cap from the filter housing.
Accordingly, an object of the present invention is to provide a high-pressure filter cap in which the threads are arranged to minimize contact with solid residue. It is also an object of the present invention to provide a high-pressure filter cap in which the threads are arranged to maximize the ability of the filter cap to withstand a high pressure differential, the seal and threads are arranged to minimize the deposit of residue on the threads, and the seal is arranged to maximize the ability of the seal to withstand a high pressure differential.